A theoretical study of the hydrolysis of a β-lactam antibiotic was carried out in gas phase at different levels of theory. Later, the reaction was studied in solution, describing the sub-set of atoms of the QM region with semiempirical and density functional theory methods while classical force fields were used to describe the explicit solvent water molecules. QM/MM Molecular Dynamics simulations were used to generate the potential of mean force for the reaction in solution. The mechanism of hydrolysis of two antibiotics were explored in the active site of a mononuclear β lactamase. QM/MM methods have been applied to the study of an enzyme belonging to the family of copper monooxygenases. In particular the mechanism of hydroxylation by peptidylglycine α-hydroxylating monooxygenase was the subject of the study. Due to the electronic complexity of the system, ab initio MD simulations were required in order to get a proper description of the reaction.
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